A recent development in third generation (3G) wireless communications is the long term evolution (LTE) cellular communication standard, sometimes referred to as 4th generation (4G) systems. Both 3G and 4G technologies are compliant with third generation partnership project (3GPP™) standards. It is expected that 4G systems will primarily be deployed within existing spectral allocations owned by Network Operators as well as new spectral allocations that are yet to be licensed. Irrespective of whether these LTE spectral allocations use existing second generation (2G) or 3G allocations that are being re-farmed for fourth generation (4G) systems, or new spectral allocations for existing mobile communications, they will be primarily paired spectrum for frequency division duplex (FDD) operation.
In addition to the large number of standard wireless subscriber communication units that employ the above technologies, there are an increasing number of other communication devices that may usefully connect to current mobile telecommunication networks. Examples of such other communication devices include so-called machine-type wireless communication (MTC) devices for MTC-based applications, which are typified by semi-autonomous or autonomous communication of small amounts of data to a central repository on a relatively infrequent basis. Examples of MTC devices include so-called smart meters, which, for example, may be located in a customer's house and periodically transmit information back to a central MTC server, for example data relating to the customer's consumption of a utility, such as gas, water, electricity and so on. Thus, a large number of MTC devices are expected to support very low power consumption operation based on intermittent transmissions of small amounts of data.
It is also known that ‘uplink-only relaying’ is a network topology that may be used to address the issue of achieving low transmit power for low-cost MTC devices, for instance, in macro cellular LTE networks. In general, in relay-node applications, there is typically sufficient system gain on the downlink (i.e. base station to subscriber communication unit or terminal device) to support MTC devices (or User Equipment (UE)) (MTC-UE) at the cell edge of the macrocell of a base station, such as an eNodeB (eNB). However, with the low transmit output power of the MTC devices, the uplink (terminal device to base station) system gain is significantly less than the downlink; hence the evolved concept of ‘uplink-only relaying’ techniques. The use of a single-hop uplink-only relay device (sometimes referred to as relay device (RN)) can be used to address this issue and close the link budget for remote subscriber communication devices, such as MTC-UEs. Typically, only a single hop may be employed, provided that the MTC-RN can be expected to have similar characteristics to an LTE UE. In a network where relay devices (also referred to herein as relay devices) are utilised to relay uplink data from the terminal devices to the eNodeB, the eNodeB may be referred to as a donor eNodeB (DeNB).
FIG. 1 illustrates a simplified schematic of an uplink only single-hop relay communication system 100, comprising base station (such as eNodeB) 105, core network 110, relay device 115 and user equipment (UE) 120. In this simplified schematic, eNodeB 105 communicates with other eNodeBs (not shown) via the core network 110. Communication system 100 comprises an asymmetric uplink/downlink arrangement, whereby wireless downlink communications between the base station 105 and UE 120 have a direct communication path 125, but are single-hopped for the uplink communication path 130 from UE 120 to base station 105 via relay device 115. The base station 105 may also transmit control signalling on a separate downlink path 135 to relay device 115 in order to control the operation of the relay device 115.
The configuration of FIG. 1 allows lower power transmissions to be sent from the UE 120, for example where the lower power is sufficient for the MTC device's lower transmit power to be able to reach the relay device's receiver at a decodable power level, whereas the MTC device's lower transmit power would not be able to reach the eNodeB's receiver at a decodable power level. However, one disadvantage with this system is that the transmission time from the UE 120 to the base station 105 has been increased due to the implementation of relay device 115. Further, there is no opportunity for a downlink transmission from the relay device 115 to the UE 120. Therefore, a potential problem with uplink-only relaying in such an asymmetric arrangement is that the relay device 115 is unable to feed back control information to the MTC device (UE 120).
Thus, at present, there is no known mechanism for the relay device 115 to influence efficient future transmissions between the MTC device and the base station 105 via the relay device 115, for example to control the power level of such transmissions to the relay device 115 in order to avoid blocking the relay device's receiver or causing interference with other users. Hence, in contrast to symmetric systems, there is no known mechanism for the UE 120 to transfer either acknowledgement/negative acknowledgement (ACK/NACK) or channel quality information (CQI) from the UE 120 to the base station 105.
Therefore, there is a need for an uplink-only relaying system to be able to better control communications from a terminal device, such as an MTC device, via a relay device, for example for the transportation of information carried on PUCCH that is subsequently relayed by the MTC relay device to a base station.